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Anglo Bellows Folds


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#19 Bob Tedrow

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Posted 04 October 2003 - 10:06 AM

Rich,

I agree that the main limiting factor is the gussets, because they in turn are influenced by the angular difference in operating plane of the adjacent run of panels.

I hope I can explain myself here:


A bellows "segment" has two transverse planes: one of fixed outside diameter, the outside fold. One of variable diameter, (of a fixed range, this is important) the inside fold.

The inside fold and outside folds are connected by the trapeziodal cards of fixed length.

There is no way (other than pulling the bellows apart and destryoing it) the inside plane can geometrically extend/expand beyond its range.

If if build a bellows endoskelton without gussets, remove it from the jig, it will extend to its maximum length and stop, dead, absolutely at its geometric limit.

The gussets do not serve to limit the movement and extension of the bellows at all.....unless they are installed short of the functional range of motion, in which case they do...and limit the extension of the bellows as a result.

Note that I am completely disregarding the flexibility of the cards themselves, which can provide a bit of vulgar and self-destructive flexibility on their own.

Gussets may be used as a "safety device" to limit the extension of the bellows and indeed this may be a good idea......because:

If the two planes of the bellows segment are not completely parallel or the cards are not glued properly in line, the plane itself will fail and the bellows will collapse or "blow out"

Poorly glued bellows cards can be recognized by a tearing sound at extreme extension, indicating delaminating of the cards.

I base the above on the strength of my experience building many bad bellows.

by golly,

Bob Tedrow

Edited by Bob Tedrow, 04 October 2003 - 12:26 PM.


#20 goran rahm

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Posted 05 October 2003 - 11:06 PM

Dave said "more folds the merrier" and I can't agree at allbecause conditions do change....Not quoting myself but repeating the essence of my previous message. The efficiency of bellowsing and fingering are both related to the stability if the 'interface' hand/instrument i.e. the 'handle since this provides the means of 'control'.

A long(many folds) bellows and a short one are evenly stable when closed and the differences appear the more they are opened and IF you work in s straght line or by fanning. Without considering these factors the whole discussion is meaningless.

The eight folded miniture Dave mentioned is manageable since the small size makes it possible to stabilize it by force. However even the miniature becomes *very* much 'better' with an improved handle. Noone has commented upon my notice about the comparison between 5 and 7 folded Anglos and the dependence on handle stability. The efficiency may be so much improved that even the problems with chord playing are reduced. TRY IT ! - everyone who is in doubt - that is the only way to learn and know....

#21 d.elliott

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Posted 07 October 2003 - 02:41 PM

Goran,

two points: English miniatures do not have any form of handle, and as to the more the merrier, I did say within reason, trusting to the good sense of the bellows manufacturer/ repairer not to over do it.

Dave

#22 JimLucas

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Posted 07 October 2003 - 03:13 PM

My Jeffries-made metal-ended Crane duet and my ebony-ended Edeophone Crane duet are essentially the same size, both with 7-fold bellows of virtually equal extension. But I find the Edeophone bellows much more difficult to control -- except at nearly full extension, -- even though the Jeffries is much heavier. The Edeophone displays a strong tendency to bend at the slightest imbalance in pressure from the hands, while the 6-sided Jeffries actually shows some resistance to non-parallel flexing, even though it has deeper folds.

I believe the geomety *is* a factor in this difference. The Jeffries also has slightly thicker leather, and I'm sure this has some effect, but watching and feeling the behavior of the two bellows, I'm convinced that it's not the dominant factor.

#23 goran rahm

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Posted 09 October 2003 - 12:29 PM

Dave, I have of course provided my miniatures with handles since they normally like you say don't have any and the difference is enourmous but that was not my point. The small size DO make them more maneuverable despite the many folds and relatively (to the diameter) long bellongs since you can stabilize the side movements by available force...not being possible with the sizes from treble and 'upwards,

Jim, I fully agree concerning the significance of number of sides and comparing 4(6) with the 12 of the Edeophone truly demonstrates it so there may be quite a few factors involved when two individual instruments are compared for stablity of bellows and its implications for playing efficiency

Goran




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